Deep-dish cheese, onion & potato pie

Name: Deep-dish cheese, onion & potato pie
Prep time: 40 min
Cook time: 1 h 30 min
Total time: 2 h 10 min
Cuisine: British
Ingredients: 200g strong, hard cheese (we used cheddar ), ½ coarsely grated, ½ cut into small chunks; 200ml tub crème fraîche; 500g shortcrust pastry; 1kg floury potatoes , thinly sliced; 2 onions , finely sliced; 1 bunch spring onions , roughly chopped; small pinch grated nutmeg; large pinch paprika; 1 egg , beaten